(1) Field of the Invention
The present invention relates to a task management function of an operating system, and in particular to a technique for determining an execution sequence of tasks.
(2) Description of the Related Art
Major functions of an operating system (OS) include hardware management, task management, data management, and input/output management. Among these, task management is a particularly important function of managing an execution sequence of tasks, for enabling efficient operations of a CPU, memory, input/output apparatus etc. A “task” is a unit of control for managing a processing flow of a program from its activation, execution, through termination etc. Programs that operate under management of the OS are treated as tasks, and execution, priority processing, parallel processing etc. of programs are all realized in units of tasks.
One of algorithms for determining an execution sequence of tasks is a “priority method”. To put it simply, the priority method is a method of determining an execution sequence of tasks based upon priorities set for the tasks.
According to a conventional priority method, however, an execution sequence of a plurality of tasks for which the same priority is set is determined in the order of arrival of the tasks. The conventional priority method therefore fails to appropriately control an execution sequence of such tasks that are given the same priority.